Shrews Shrink Their Skull To Survive Winter: Study

Scientists have found out that shrews change their size according to season, to possibly conserve energy as a survival tactic to withstand winter. A new study shows that the tiny gray mammals can get rid of 20 percent of their body size during cold months.

The Changing Of The Shrews

Shrews are known to be smaller in size during winter as compared with summer months — a fact that researchers have known for long. However, the reason behind the science of the changing size was unknown. In fact, ecologists also believed that the bigger shrews died during cold winter months.

To know more about the changing size mystery of shrews, a research team captured shrews with live traps in Germany. The process of capturing, releasing and then recapturing shrews was repeated numerous times throughout the year.

One hundred live common shrews were caught during the exercise, 37 of which were recaptured repeatedly. The researchers noticed a visible pattern in the 37 shrews caught multiple times — they were becoming bigger during the summer and smaller during the winter.

Incidentally, the scientists took the help of X-rays and computer imaging to observe the size of the shrews’ brains and skeletons.

“We don’t know why for sure why this happens,” said researcher Javier Lázaro from Max Planck Institute for Ornithology. “We hypothesize that they have developed these shrinkings to face the winter months when they have less food,” he added.

The Change In Size Also Affects The Skull Of Shrews

The researchers were surprised to observe that as the skeleton of the shrews shrinks, so do their skulls — and consequently, their brain case and brain. However, at present, there is no further research that explains whether the shrunken brain impacts the intelligence of shrews.

The muscles, fat, heart, liver, spleen and spine of the shrews also shrunk and regrew, the study further notes. The researchers noticed that at summer, a young shrew weighs about 8 grams, while during winter, it weighs only about 6 grams. Furthermore, a summer adult shrew gained twice the body mass to weigh approximately 14 to 15 grams.

Lázaro added that the researchers are dealing with a system that loses bone tissues and then allows these tissues to regenerate in some still unknown mechanism. The researchers also noted that the study shows a significant evolutionary mechanism that could have wide-ranging implications, which could impact medicinal development for humans too.

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